This proposal requests funds to purchase a JEOL 200 CX transmission electron microscope to serve as a research instrument for 2 NIH funded co-investigators and additional users. This instrument offers multiple accelerating voltages up to 200 KV which permits the use of thicker sections. This instrument will be used in the examination of a variety of tissues by conventional thin sections as well as thicker sections. The examination of thick sections at 200 KV with the goniometer stage allows the investigator to use stereo pair photographs for the 3-dimensional analysis of tissue. This instrument will be a state of the art instrument and is necessary to update the present instrument, a JEOL 100B, which is 9 years old and has received heavy use. This instrument will require less maintenance and yield better resolution with both thin and thick sections of tissue. This instrument will be housed in the Electron Microscopy Laboratory of the School of Medicine.